The music is Siegfried's funeral march from Gotterdammerung (twilight of the gods). Speaking very generally, Siegfried symbolizes Germany and his death (stabbed in the back) is one of the very last in a long line of events resulting in the collapse of the old world order (twilight of the gods - i.e. ragnorok) and the emergence of humanity (at least in my interpretation). I see this emergence as embodying a kind of tabula rasa purity. We have a chance to do things right, this time.